McDonald’s will require suppliers to improve the living conditions and slaughter process for chickens raised to be served in its restaurants, the company said on Friday, in the latest changes affecting popular menu items like McNuggets.

Under new guidelines for animal welfare, suppliers such as Tyson Foods and Cargill must by 2024 meet new standards for the amount and brightness of light in chicken houses, provide access to perches that promote natural behaviour among birds, and take other steps, according to McDonald’s.

The fast-food chain said it will set targets for chickens’ health, including how well they walk and whether they have broken wings, and use third-party audits to ensure that farms comply. It will work with suppliers and technology companies to develop monitoring systems that automatically gather data on chickens’ behaviour on farms.

Such requirements often raise costs for chicken producers because they must buy new equipment and retrofit chicken houses to comply. However, McDonald’s said it would not raise menu prices as a result. Tyson and Cargill said they supported McDonald’s moves.

The requirements are the latest changes to affect McDonald’s menu that address consumers’ concerns about human and animal health. The company previously stopped buying chicken meat for US restaurants from birds raised with antibiotics that are important to human health and said it would shift to using cage-free eggs in the US and Canada.

The world’s largest restaurant chain by revenue has been working to boost flagging traffic at its US restaurants, where it gets most of its profit, after customers defected to fast-food rivals.

“While this might not be a direct impact on sales at McDonald’s, it might help certain segments of our customer base make purchasing decisions that they might not have otherwise made,” Bruce Feinberg, a senior director for McDonald’s who works on meat products, said about the new standards.

Under the changes, McDonald’s also will buy chickens in the United States and Canada that have been rendered unconscious before slaughter with gas, instead of with electricity, a process some consider more humane.

The changes cover birds that account for more than 70 per cent of McDonald’s global chicken supply, according to the company. It declined to reveal the number of chickens.

“I think it’s one of the most comprehensive programmes that I’ve seen for chickens,” said livestock researcher Temple Grandin, who pioneered humane slaughterhouse practises and works with McDonald’s.